The present invention relates to apparatus for cleaning finishing machines of a type having a generally cylindrical screen for removing solids from juice or the like, and more particularly to such apparatus adapted for automatically cleaning extrusion screens of such finishing machines with little or no interruption in the normal operating cycle of the finishing machine. It is particularly contemplated that the apparatus of the present invention be employed in connection with the finishing of initial juices obtained from fruits, particularly citrus fruits, and vegetables such as tomatoes.
In the production of juices from various fruits and vegetables, juice extraction machines are commonly employed to first obtain an initial or raw juice containing substantial amounts of various solids such a rag, pulp from juice sacs, pectinous material, seeds, etc. Typical examples of juice extraction machines for obtaining initial or raw juice from various fruits and vegetables are disclosed, for example, in U.S. Pat. Nos. 2,631,625 and 4,170,935. The construction and method of operation contemplated for these machines is not of particular concern in connection with the present invention. Rather, the above-noted patents are referred to herein only for the purpose of demonstrating an exemplary source for the initial or raw juice with which the method and apparatus of the present invention are contemplated for use.
In order to produce commercially desirable juice from the initial or raw juice obtained from juice extraction machines, it is generally necessary or desirable to first remove a substantial portion of the solid components from the initial juice to provide a so-called finished juice.
A typical commercial machine for converting initial or raw juice to a finished juice, characterized as being a screw-type finisher, is disclosed, for example, in Holbrook U.S. Pat. No. 3,370,527. In a finisher of this type, the initial juice or slurry is introduced into the interior of a stationary cylindrical screen. The screen is in effect a thin-walled cylindrical member, preferably formed from stainless steel, with very small, closely spaced extrusion openings formed about its circumference and along its length.
A rotary screw is designed to have a fairly close tolerance fit within the screen. The screw is rotated to conduct the initial juice or slurry along the length of the screen, forcing a liquid juice portion through the screen while a substantial portion of solids from the initial juice is retained upon the screen and conducted to a point of discharge. The finishing machine of the above-noted patent is described in greater detail below.
It is to be noted that the present invention is not limited to a particular type of finisher or even to a general screw-type finisher as described above. For example, screw-type finishers tend to be of two different types. In one type, the screen and the outside diameter of the relatively rotating screw element are tapered with the smaller diameter being located at the discharge end. The rotary screw is tapered and the pitch of its flights varies so that the cross sectional area between the flights decreases at the discharge end.
In other screw-type finishers, the screen and the outside diameter of the screw are cylindrical. The rotary screw may be conical with the large diameter at the discharge end, or the rotary screw may be cylindrical.
In both of the above screw-type finishers, a pneumatically operated pulp escape valve is provided at the discharge end of the screen. As the fluid or juice component from the initial juice or slurry passes through the screen, substantial solids build up on the screen, particularly at the discharge end. The valve is commonly regulated in order to properly control the slurry solids.
In yet another type of finisher, commonly referred to as a paddle-type finisher, the initial juice or slurry is also introduced into the interior of a stationary screen which is conical or cylindrical in shape. A paddle device is rotated within the interior of the cylindrical screen and serves a similar function as the screw element in the screw-type finishers for conveying the initial juice or slurry along the screen. A liquid portion of the juice passes through the screen with remaining solids being conducted along the interior of the screen toward a solids outlet.
In any event, regardless of the particular type of finishing machine employed, the solids from the intial juice tend to build upon the screen and to plug the openings, thus tending to interfere with its continued operation. In the past it has generally been necessary to shut down finishing operations of the machines and to remove the solids from the screen, for example, by manually directing fluid or liquid at the screen in order to clean the openings in the screen and to rinse solids from the surfaces of the screen.
Although these manual cleaning steps have been found suitable for conditioning the finishers for continued operation, they have been found to be unsatisfactory because of lost operating time for the finishing machines and overall efficiency. This loss in efficiency is particularly apparent when large numbers of finishing machines are employed in single installations. In such situations, the need to individually shut down the finishing machines and carry out manual operations as described above has been particularly time consuming and inefficient.
In any event, there has been found to remain a need for an improved method and apparatus for cleaning such finishing machines.